1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same and more particularly to a semiconductor device provided with a pad metal film to which a conductor for external connection to be connected to external wiring formed on a printed circuit board is fitted and wherein the pad metal film is covered, except a face for fitting the conductor for external connection, with a final protective insulating film.
2. Description of the Related Art
As the integration of an LSI (Large Scale Integrated Circuit) used for a microprocessor or memory, known as a typical semiconductor device increases, each region of such semiconductors constituting the LSI is being scaled down dimensionally. In wiring processes for each region of the semiconductor, an interconnection hole including a contact hole or via hole formed on an insulating film and a trench for interconnection into which wiring is imbedded are dimensionally scaled down as well. In response to higher wiring density, multi-level interconnect technology by which the wiring is multi-layered in the direction of a thickness of a semiconductor substrate is developing. In the updated LSI, a multi-level interconnect (for example, 5 to 7 levels) has been incorporated. In such LSIs, if used for a high-speed microprocessor in particular, a resistance value of wiring presents a problem in terms of operations. Wiring having less resistance is desired accordingly. Conventionally, as a material for wiring in semiconductor devices including LSIs, aluminum or aluminum metal composed mainly of aluminum being excellent in electric characteristics, processabilities and the like. However, aluminum metals have a shortcoming of being less resistant to electromigration and to stress migration. Because of this, there is a tendency that copper or copper metals composed mainly of copper, which is of less resistance compared with aluminum and is excellent in resistance against electromigration and stress migration, are used instead of aluminum.
FIG. 9 is a cross-sectional view showing a conventional semiconductor device (hereafter referred to as a first conventional example). In the conventional semiconductor substrate 65 in FIG. 9, a trench for interconnect 53 is formed in a protective insulating film 52 formed on a semiconductor substrate 51 and on the trench for interconnect is formed a uppermost-layered copper wiring 55 through a first barrier metal film 54 composed of a titanium nitride film or the like. The protective insulating film 52 is covered with a final protective insulating film 56 and in the final protective insulating film 56 is formed a contact hole 57 with an approximately central part of the uppermost-layered copper wiring 55 exposed. In this contact hole 57 is formed a second barrier metal film 58 composed of stacked layers containing, for example, a titanium nitride film, a nickel film and a gold film and through this second barrier metal film 58 is formed a copper pad metal film 59. To this copper pad metal film 59 is fitted a bump-like conductor 60 composed of solder.
The first barrier metal film 54 is used to prevent adverse effects on the lower-layered wiring or diffused region caused by diffusion of the uppermost-layered copper wiring 55 into the protective insulating film 52. Moreover, the second barrier metal film 58 is used to prevent the inconvenience of copper suctioning or the like caused by an action of solder components of the bump-like conductor 60.
As shown in FIG. 16, a semiconductor device 65 is mounted, by a flip chip method (face-down bonding), on an external wiring 62 fitted to a printed circuit board 61 through a bump-like conductor 60 to be served as a conductor for external connection which is connected to the uppermost-layered copper wiring 55.
Referring to FIGS. 10A, 10B, 10C, 11A, 11B, 11A and 12B, a method for manufacturing the first conventional example of the semiconductor device is described hereinafter in order of processes.
First, as shown in FIG. 10A, a trench for interconnect 53 is formed on a protective insulating film 52 mounted on a semiconductor substrate 51 by using lithography technology. Next, as shown in FIG. 10B, on the protection insulating film 52 containing the trench for interconnect 53 are sequentially formed the first barrier metal film 54 and uppermost-layered copper wiring film 55A by using a sputtering method or the like.
Next, as shown in FIG. 10C, by removing both the first barrier metal film 54 and the uppermost-layered copper wiring film 55 from the upper face of both the protective insulating film 52 and the trench for interconnect 53 using a CMP (Chemical Mechanical Polishing) method, the protective insulating film 52 is planarized in order to form the uppermost-layered copper wiring 55.
Next, as shown in FIG. 11A, after the formation of a final protective insulating film 56 on the protective insulating film 52, a resist film 63 is formed. Then, as depicted in FIG. 11B, by using the resist film 63 as a mask, etching on the final protective insulating film 56 is performed to provide the contact hole 57. Next, as shown in FIG. 12A, after the sequential formation of the second barrier metal film 58 and copper pad metal film 59, a resist film 64 is formed. Furthermore, as shown in FIG. 12B, using the resist film 64 as a mask, patterning of the second barrier metal film 58 and the copper pad metal film 59 to a desired shape are performed. Then, by using a plating method, a bump-like conductor 60 composed of solder is fitted to the pad metal film 59 to produce a semiconductor device shown in FIG. 9.
FIG. 13 is a cross-sectional view showing a conventional semiconductor device (hereinafter referred to as a second conventional example). As shown in FIG. 13, in a semiconductor device 70, an aluminum pad metal film 66 is formed, through the second barrier metal film 58, on the first barrier metal film 54 and uppermost-layered copper wiring 55. To the aluminum pad metal film 66 is fitted a wire-like conductor 67 composed of aluminum. In this example, the second barrier metal film 58 serves to prevent a reaction between the uppermost-layered copper wiring 55 and the aluminum pad metal film 66. The same reference numbers in FIG. 13 designate corresponding parts shown in FIG. 9 and the description is omitted
The semiconductor device 70, as shown in FIG. 17, is fixed, by face-up bonding, on a printed circuit board 61 using an adhesive agent and is then mounted on an external wiring 62 through a wire-like conductor 67 used as a conductor for external connection.
By referring to FIGS. 14A, 14B, 15A and 15B, a method for manufacturing a second conventional example of semiconductor devices.
First, as shown in FIG. 14A, after the second barrier metal film 58 and the aluminum pad metal film 66 obtained in FIG. 10C are formed on a protective insulating film 52, the first barrier metal film 54 and the uppermost-layered copper wiring 55, a resist film 68 is formed. Next, as shown in FIG. 14B, using the resist film 68 as a mask, patterning of the second barrier metal film 58 and aluminum pad metal film 66 to a desired shape is performed.
Next, as depicted in FIG. 15A, after the formation of the final protective insulating film 56 on the protective insulating film 52 and aluminum pad metal film 66, a resist film 69 is formed. Then, as shown in FIG. 15B, using the resist film 69 as a mask, patterning of the final protective insulating film 56 to a desired shape is performed to make the aluminum pad metal film 66 exposed. Then, by using a wire bonding method, a wire-like conductor 67 composed of aluminum is fitted to the aluminum pad metal film 66 to produce the semiconductor device shown in FIG. 9.
In the conventional first and second examples of the semiconductor devices, there is a problem in that they require many numbers of processes to produce them.
That is, in the first conventional example, the trench for interconnect 53 is, in advance, formed on the protective insulating film 52 and the uppermost-layered copper wiring 55 is formed through the first barrier metal film 54. Then, the final protective insulating film 56 is formed to provide the contact hole 57. Furthermore, after the formation of the second barrier metal film 58 and the pad metal film 59, patterning of the pad metal film 59 is performed. Accordingly, many numbers of processes are required to obtain the pad metal film 59.
Furthermore, in the second conventional example as in the first conventional one, the trench for interconnect 53 is formed, in advance, on the protective insulating film 52 and the uppermost-layered copper wiring 55 is formed through the first barrier metal film 54. Then, after the formation of the second barrier metal film 58 and aluminum pad metal film 66, the patterning of the aluminum pad metal film is performed. Accordingly, the increase in numbers of processes is unavoidable.
In view of the above, it is an object of the present invention to provide a semiconductor device and a method for manufacturing the same wherein an uppermost-layered copper wiring has barrier metal films both at an interface with a pad metal film and at an interface with backing insulating film and wherein the pad metal film used to fit a conductor for external connection, composed of a bump-like or wire-like conductor, can be formed by reduced numbers of processes.
According to a first aspect of the present invention, there is provided a semiconductor device comprising a pad metal film to which a conductor for external connection to be connected to an external wiring formed on printed circuit boards is fitted and which is covered, except a face for fitting the conductor for external connection, with a final protective insulating film and which is connected to the uppermost-layered wiring;
whereby the uppermost-layered wiring being provided with the pad metal film through a second barrier metal film and with the first barrier metal film at an opposite face to the pad metal film.
In the foregoing, a preferable mode is one wherein the protective insulating film is formed below the final protective insulating film and on the protective insulating film are formed, from the bottom, the first barrier metal film, the uppermost-layered wiring film, the second barrier metal film and the pad metal film.
According to a second aspect of the present invention, there is provided a semiconductor device comprising a pad metal film to which a conductor for external connection to be connected to an external wiring formed on printed circuit boards and which is covered, except a face for fitting the conductor for external connection, with a final protective insulating film and which is connected to an uppermost-layered wiring;
whereby a protective insulating film being formed below the final protective insulating film and on the protective insulating film is formed a trench for interconnect with a first barrier metal film, the uppermost-layered wiring, a second barrier metal film and the pad metal film imbedded from the bottom.
In the foregoing, it is preferable that the uppermost-layered wiring comprises a metal film composed mainly of copper.
Also, it is preferable that the conductor for external connection is composed of a bump-like conductor.
Also, it is preferable that the conductor for external connection is composed of a wire-like conductor.
Also, it is preferable that the bump-like conductor comprises solder or a metal composed mainly of gold.
A preferable mode is one wherein the wire-like conductor comprises aluminum or a metal composed of gold.
Also, a preferable mode is one wherein the pad metal film comprises a metal composed mainly of copper.
Also, a preferable mode is one wherein the pad metal film comprises a metal composed mainly of aluminum.
According to a third aspect of the present invention, there is provided a method for manufacturing a semiconductor device comprising the steps of:
forming a trench for interconnect on a protective insulating film provided on a semiconductor substrate;
forming metal films including, in order, a first barrier metal film, uppermost-layered wiring film, second barrier metal film and pad metal film on said protective insulating film including said trench for interconnect;
planarizing the protective insulating film by removing the first barrier metal film, uppermost-layered wiring film, second barrier metal film and the pad metal film from an upper face of the protective insulating film and the trench for interconnect;
patterning a final protective insulating film, after forming the final protective insulating film on the planarized protective insulating film, so that only the surface of the pad metal film is exposed; and
fitting a conductor for external connection on the exposed area of the pad metal film.
According to a fourth aspect of the present invention, there is provided a method for manufacturing a semiconductor device comprising the steps of:
forming metal films including, in order, a first barrier metal film, uppermost-layered wiring film, second barrier metal film and pad metal film on a protective insulating film on a semiconductor substrate;
patterning the first barrier metal film, uppermost-layered wiring film, second barrier metal film and the pad metal film on the surface of the protective insulating film to desired shapes;
patterning a final protective insulating film, after forming the final protective insulating film on the patterned metal film, so that only the surface of the pad metal film is exposed; and
fitting a conductor for external connection on the exposed surface of the pad metal film.
In the foregoing, a preferable mode is one wherein a metal film composed mainly of copper is used as the uppermost-layered wiring film.
Also, a preferable mode is one wherein a bump-like conductor is used as a conductor for external connection.
Also, a preferable mode is one wherein a wire-like conductor is used as a conductor for external connection.
It is preferable that a metal composed mainly of copper as the pad metal film.
Furthermore, it is preferable that a metal composed mainly of aluminum as the pad metal film.